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Ecological site R024XY125OR

SEMI PONDED LAKEBED

Accessed: 05/05/2026

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General information

Draft. A draft ecological site description is either incomplete or has not undergone quality control and quality assurance review.

Ecological site concept

No soils are correlated to this ecological site. Ecological site concept should be evaluated.

Associated sites

R010XY004OR	Meadow Meadow (longer duration suface saturation, higher water table, greater production, different composition – DECA18- CAREX-JUNCU association)
R023XY100OR	LAKEBED Lakebed (frequent ponding to greater depth and longer duration – greater than 2 feet 3 in 10 years, different composition-ELEOC/RUMEX/JUARL association)
R024XY004OR	DRY FLOODPLAIN 6-10 PZ Dry Floodplain (moderately well to well drained, higher production, different composition-ARTRT/LECI4-LETR5 association)
R024XY006OR	LAKE TERRACE Lake Terrace (drier, different composition LETR5 strongly dominant)
R024XY007OR	DRY PONDED CLAY 6-10 PZ Dry Ponded Clay 6-10 PZ (drier, different composition - ARTRT/LETR5 association)
R024XY008OR	CLAYEY PLAYETTE Clayey Playette (droughty, lower production, different composition- ARTRW8/ELEL5-POSE association)
R024XY123OR	LOW CLAYEY TERRACE 8-10 PZ Low Clayey Terrace 8-10 PZ (well drained, lower production, different composition - ARTRW8/PSSPS-POSE association)
R024XY126OR	FLOODED CLAY SWALE Flooded Clay Swale (lower swale and overflow channel position, longer flooding duration, somewhat poorly drained, higher production, different composition- ARCA13/PONE-LETR5 association)

Similar sites

R024XY007OR	DRY PONDED CLAY 6-10 PZ Dry Ponded Clay 6-10 PZ (drier, different composition- ARTRT/LETR5 association)
R023XY100OR	LAKEBED Lakebed (frequent ponding to greater depth and longer duration –greater than 2 feet 3 in 10 years, different composition-ELEOC/RUMEX/JUARL association)
R023XY200OR	PONDED CLAY Ponded Clay (upland depression position, longer duration shallow ponding, different composition - ARCA13 present)
R010XY004OR	Meadow Meadow (longer duration suface saturation, higher water table, greater production, different composition – DECA18-CAREX-JUNCU association)

Table 1. Dominant plant species

Tree	Not specified
Shrub	Not specified
Herbaceous	(1) Muhlenbergia richardsonis (2) Poa nevadensis

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Physiographic features

This site occurs in small to large lake basins that are occasionally ponded to a shallow depth from spring runoff. The annual surface extent of ponding is highly variable. Extended long duration deep ponding (less than 2 feet) is rare, occurring one in ten or more years and is of a weather dependent cyclical nature. Slopes range from 0 to 1 percent. Elevations range from 4000 to 4500 feet.

Table 2. Representative physiographic features

Landforms	(1) Basin floor (2) Lakebed (3) Pluvial lake (relict)
Ponding duration	Very brief (4 to 48 hours) to brief (2 to 7 days)
Ponding frequency	Occasional to rare
Elevation	4000 – 4600 ft
Slope	0 – 3 %
Water table depth	30 – 60 in
Aspect	Aspect is not a significant factor

Climatic features

The annual precipitation ranges from 6 to 10 inches, most of which occurs in the form of rain and snow during the months of December through April. Additional moisture is cyclically supplied to the site by spring run-off from surrounding upland sites. The soil temperature is mesic to frigid near mesic with a mean air temperature of 47 degrees F. Temperature extremes range from 100 to -10 degrees F. The frost-free period ranges from 80 to 120 days. The optimum period for plant growth is from late April to early July.

Table 3 Representative climatic features

Frost-free period (average)	120 days
Freeze-free period (average)	0 days
Precipitation total (average)	10 in

Bar

Line

Figure 1. Monthly precipitation range

Bar

Line

Figure 2. Monthly average minimum and maximum temperature

Soil features

The soils of this site are typically fine textured, very deep and somewhat poorly drained. A thin organic layer less than 2 inches deep is over a clay loam surface over a clayey subsoil. Substratums are lacustrine sediments. Shallow ponding cyclically occurs for short periods in the spring. Longer duration deep ponding is infrequent. Permeability is very slow. The availabe water holding capacity (AWC) is 5 to 10 inches. A periodic high water table restricts the rooting depth. The water erosion potential is slight due to the low elevation flat position of the site.

Table 4. Representative soil features

Parent material	(1) Lacustrine deposits – rhyolite (2) Eolian deposits – basalt
Surface texture	(1) Clay loam
Family particle size	(1) Clayey
Drainage class	Somewhat poorly drained to poorly drained
Permeability class	Very slow to slow
Soil depth	72 – 0 in
Available water capacity (0-40in)	6 – 8 in

Ecological dynamics

The potential native plant community is dominated by mat muhly and Nevada bluegrass. Spike rush and baltic rush occur. Dock and
a variety of other forbs are present. Vegetative composition is about 85 percent grass/grass-like and 15 percent forbs. The approximate ground cover is 60 to 80 percent (basal and crown).

Range in Characteristics-
Variability in plant composition and production on this site results from differences in short duration annual and longer duration episodic (10 year +/-) ponding events. With the typical annual short duration ponding, micro-relief and related sub-surface water availability has an important influence on plant composition. Nevada bluegrass increases in low meandering channels and ponded areas. Mat muhly increases in drier areas. Spike rush, sedges and rushes increase where water collects for a longer period of time. With infrequent longer duration deep ponding these differences are masked. Spike rush and other obligate wetland species increase for a short period of time and shrub encroachment from associated sites is eliminated.

Response to Disturbance-
Deterioration of the site can result from both hydrologic alterations and overgrazing. Hydrologic alteration impacts can occur from off-site and on-site activities. These activities include upstream water withdrawals for agriculture needs, channel realignment for transportation corridors, channel diversions and blockages and partial conversion of the lakebed to agriculture use. Limited hydrologic alterations occur with the construction of dugouts to concentrate water for extended seasonal livestock water. In all cases the site becomes drier with varying decreases or loss of plants adapted to wetlands.

When heavy grazing causes site deterioration, Nevada bluegrass rapidly decreases and mat muhly increases. With continued deterioration mat muhly, spike rush and Baltic rush decrease. Forbs increase, areas of bare ground increase and annuals invade or increase. Annual grasses including ventenata an invader and annual tufted hairgrass are strong inceasers.

States: MURI-annual grasses/forbs– bare ground; annual grasses/forbs-bare ground

State and transition model

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Ecosystem states

1. Reference Plant Community

State 1 submodel, plant communities

1.1. Reference Plant Community

State 1
Reference Plant Community

Community 1.1
Reference Plant Community

The reference native plant community is dominated by mat muhly and Nevada bluegrass. Spike rush and baltic rush are common. Dock and a variety of other forbs are present. Vegetative composition is about 85 percent grass/grass-like and 15 percent forbs. The approximate ground cover is 60 to 80 percent (basal and crown).

Figure 3. Annual production by plant type (representative values) or group (midpoint values)

Table 5. Annual production by plant type

Plant type	Low (lb/acre)	Representative value (lb/acre)	High (lb/acre)
Grass/Grasslike	595	935	1360
Forb	105	165	240
Total	700	1100	1600

Additional community tables

Table 6. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production ()	Foliar cover (%)
Grass/Grasslike
1	Dominant, moderate-rooted, rhizomatous grass			330–550
	mat muhly	MURI	Muhlenbergia richardsonis	330–550	–
2	Sub-dominant, moderate rooted, bunchgrass			220–330
3	Moderate rooted, rhizomatous grass-like			180–385
	spikerush	ELEOC	Eleocharis	110–220	–
	mountain rush	JUARL	Juncus arcticus ssp. littoralis	55–110	–
	sedge	CAREX	Carex	22–55	–
5	Other perennial grasses			20–90
	beardless wildrye	LETR5	Leymus triticoides	0–55	–
	saltgrass	DISP	Distichlis spicata	0–22	–
	squirreltail	ELEL5	Elymus elymoides	0–22	–
Forb
6	Dominant, perennial forbs			77–165
	dock	RUMEX	Rumex	55–110	–
	povertyweed	IVAX	Iva axillaris	22–55	–
7	Other perennial forbs			20–80
	arnica	ARNIC	Arnica	5–15	–
	evening primrose	OENOT	Oenothera	5–15	–
	knotweed	POLYG4	Polygonum	5–15	–
	candytuft	SMELO	Smelowskia	5–15	–
	fiveleaf clover	TRAN	Trifolium andersonii	5–15	–

Interpretations

Animal community

Livestock grazing-
This site is suited to summer and fall use by cattle, sheep, and horses under a planned grazing system. The key species are Nevada bluegrass and secondarily mat muhly. These species, particularly Nevada bluegrass can be damaged if heavily grazed during periods of flowering and seed formation before root reserves have accumulated. Plant crowns can be damaged if grazed during spring periods while the soils are wet. Deferred grazing or rest is recommended at least once every three years.

Wildlife-
This site provides water for numerous species of wildlife and waterfowl when ponded. Antelope prefer this site and make excellent use of it when forage is readily available. Various species use this site during the fall and winter. Cover is limited.

Hydrological functions

Watershed-
The soils of this site are typically near the lowest topographic position and when ponded have little runoff potential. Shallow ponding is extensive because of very low soil intake rates. The hydrologic cover condition is good when the ecological condition is high. Hydrologic cover is high when Nevada bluegrass and mat muhly components are greater than 70 percent of potential. The soils are in hydrologic group D.

Other information

This site has poor potential for range seeding because of ponding, clayey subsoils and the present lack of Nevada bluegrass and mat muhly seed.

Rangeland health reference sheet

Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.

Author(s)/participant(s)
Contact for lead author
Date
Approved by
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Presence of water flow patterns:
Number and height of erosional pedestals or terracettes:
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Number of gullies and erosion associated with gullies:
Extent of wind scoured, blowouts and/or depositional areas:
Amount of litter movement (describe size and distance expected to travel):
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):

Dominant:

Sub-dominant:

Other:

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Perennial plant reproductive capability:

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